1. Field of the Invention
The present invention relates generally to mobile electronics, and more particularly to a land vehicle navigation method and apparatus for providing route guidance by setting a destination and pass-through points. The invention also relates to storage media with encoded programs for execution of routines including a pass-through point judgment.
2. Description of the Prior Art
In conventional vehicle navigation apparatus, route guidance has been performed by setting a destination, pass-through point, facility to be seen and the like via telephone input, fifty-character voice unit input, and other types of input. In such systems places and locations are registered in advance as memory locations, thereby allowing these registered locations to be later used in setting the destination and pass-through point(s).
By way of example, responsive to an input operation effected by moving a cursor to a given location (memory location) on the guidance screen of the vehicle navigation apparatus, using a remote controller or the like, a mode selection menu with destination, pass-through point, memory, and present position is displayed as shown in FIG. 10. If "memory" is selected from the menu, then a search is initiated to identify the facility nearest the cursor position and, after it is located, the facility name "ABC", is displayed along with its register number, mark, telephone number, etc. as shown in FIG. 11 whereby upon depression of a memory button, this facility will be registered as a memory location. The location as registered in this way becomes displayable in a list format; for example, a list is displayed as shown in FIG. 10, allowing this memory location to be set as a destination upon depression of a destination button, or alternatively as a pass-through point upon depression of a pass-through point button.
With a pass-through point P is set in a guidance route as shown in FIG. 12, when a vehicle travelling along a first route R1 enters the area within a circle (pass-through judgment area) of a radius r, centered on the pass-through point P, e.g. a circle measuring 50 m in radius as shown in FIG. 12A, the system assumes that the vehicle will pass through point P and switches the route segment under guidance to the first section of a second route R2. In this way, it will not be judged that the vehicle has actually passed through point P unless it enters a pass-through judgment area extremely small in size. In other words, if the vehicle leaves first route R1 without entering the pass-through judgment area as shown in FIG. 12B, the apparatus may automatically begin searching for a route reconnecting to the first route R1 for travel toward the pass-through point P. Accordingly, even when an attempt is made before the pass-through judgment area to change or modify the travel plan to guidance for the second route without passing through point P, an intended route for connection to the second route R2 will not be searched while the system continues to search for a route reconnecting to the first route R1, unless the operator performs extra operations. For example, where it is desired to switch to the guidance relating to the second route R2, the prior art system may require that a search be again executed based on selections made from the menu presented on the guidance screen.
As is apparent from the foregoing, the vehicle does not always pass through the preset pass-through point. For instance, a situation may occur wherein a certain pass-through point has been preset as a rest stop near the mid-point of travel to a destination, but the driver has changed his mind after taking a rest prior to reaching that pass-through point and wishes to go directly to the destination without stopping at the preset pass-through point. In such a situation, the prior art apparatus requires an extra or additional operations for erasing the preset path-through point and for effecting a search for a new route to the destination, which extra operations represent an increase in complexity.